ShmoopTube
Where Monty Python meets your 10th grade teacher.
Search Thousands of Shmoop Videos
Number Sense Videos 30 videos
Number Sense: Drill Set 2, Problem 5. By what percent did his percentage grade increase from one test to the other?
Number Sense: Drill Set 3, Problem 1. This is a decrease of, approximately, what percent?
Number Sense Drill 3 Problem 3. How much interest will Warren have earned in three years?
CAHSEE Math 4.4 Number Sense 195 Views
Share It!
Description:
Number Sense: Drill Set 4, Problem 4. Solve the expression.
Transcript
- 00:03
Here's your shmoop du jour.
- 00:06
2/5 divided by... 1/15 minus 3/10 equals...what?
- 00:12
And here are the potential answers...
- 00:16
Well, this question isn't big on words -- it's just asking whether we can subtract and divide fractions.
- 00:21
Piece of cake. Because we don't want to make PEMDAS mad,
Full Transcript
- 00:24
we start with the junk inside the parentheses.
- 00:28
First we have to get a common denominator for 15 and 10.
- 00:34
Both fit into 30 pretty easily... in that case, let's multiply top and bottom of 1
- 00:38
over 15 by 2 to become 2 over 30...
- 00:43
...then we multiply top and bottom of 3 over 10 by 3 to get 9 over 30.
- 00:49
2 minus 9 is -7... so we can rewrite the problem now as 2 fifths divided by -7 over 30.
- 00:56
And remember that dividing by a fraction is the same thing as multiplying by its inverse.
- 01:01
So rewrite the problem as:
- 01:03
Two fifths TIMES -30 over 7
- 01:07
And we have -60 over 35
- 01:10
We can reduce that bad boy to -12 over 7 and voila -- it's answer A.
- 01:15
Thank goodness. Now we won't have to deal with the wrath of PEMDAS.
Related Videos
CAHSEE Math: Algebra and Functions Drill 5, Problem 3. Solve the equation.
It's impressive that these expressions are able to stay so rational even when they're having operations performed on them.
Jack and Jill went up the hill to fetch a pail of water. But what happened when they got up there? They’ve been gone an awfully long time…
